Modified block copolymers functionalized in the monoalkenyl aromatic or vinylarene block

ABSTRACT

The present invention relates to a thermally stable modified selectively hydrogenated high 1,2 content block copolymer wherein a functional group is grafted to the block copolymer in the vinylarene block.

This is a continuation of application Ser. No. 06/766,217, filed Aug.16, 1985, now abandoned.

This invention relates to novel selectively hydrogenated functionalizedblock copolymers. More particularly, it relates to a modifiedthermoplastic polymer with excellent appearance properties andmechanical properties particularly useful in blending with otherpolymers obtained by modifying a block copolymer composed of aconjugated diene compound and an aromatic vinyl compound with afunctional group grafted primarily in the vinylarene block.

BACKGROUND OF THE INVENTION

This application is related to application Ser. No. K-4723 which hasbeen filed concurrently herewith.

It is known that a block copolymer can be obtained by an anioniccopolymerization of a conjugated diene compound and an aromatic vinylcompound by using an organic alkali metal initiator. These types ofblock copolymers are diversified in characteristics, depending on thecontent of the aromatic vinyl compound.

When the content of the aromatic vinyl compound is small, the producedblock copolymer is a so-called thermoplastic rubber. It is a very usefulpolymer which shows rubber elasticity in the unvulcanized state and isapplicable for various uses such as moldings of shoe sole, etc.; impactmodifier for polystyrene resins; adhesive; binder; etc.

The block copolymers with a high aromatic vinyl compound content, suchas more than 70% by weight, provide a resin possessing both excellentimpact resistance and transparency, and such a resin is widely used inthe field of packaging. Many proposals have been made on processes forthe preparation of these types of block copolymers (U.S. Pat. No.3,639,517).

The elastomeric properties of certain aromatic vinyl polymers alsoappear to be due in part to their degree of branching. While thearomatic vinyl polymers have a basic straight carbon chain backbone,those with elastomeric properties always have pendant alkyl radicals.For example, EPR (ethylene-propylene rubber) has a structure of pendantmethyl radicals which appear to provide elasticity and other elastomericproperties. When an essentially unbranched straight chain polymer isformed, such as some polyethylenes, the resulting polymer is essentiallynon-elastomeric or in the other words relatively rigid, and behaves likea typical thermoplastic without possessing rubber-like resilience orhigh elongation, tensile strength without yield, low set or otherproperties characteristic of desirable elastomers.

Block copolymers have been produced, see U.S. Pat. No. Re. 27,145 whichcomprise primarily those having a general structure

    A--B--A

wherein the two terminal polymer blocks A comprise thermoplastic polymerblocks of vinylarenes such as polystyrene, while block B is a polymerblock of a selectively hydrogenated conjugated diene. The proportion ofthe thermoplastic terminal blocks to the center elastomeric polymerblock and the relative molecular weights of each of these blocks isbalanced to obtain a rubber having an optimum combination of propertiessuch that it behaves as a vulcanized rubber without requiring the actualstep of vulcanization. Moreover, these block copolymers can be designednot only with this important advantage but also so as to be handled inthermoplastic forming equipment and are soluble in a variety ofrelatively low cost solvents.

While these block copolymers have a number of outstanding technicaladvantages, one of their principal limitations lies in their sensitivityto oxidation. This was due to their unsaturated character which can beminimized by hydrogenating the copolymer, especially in the centersection comprising the polymeric diene block. Hydrogenation may beeffected selectively as disclosed in U.S. Pat. No. Re. 27,145. Thesepolymers are hydrogenated block copolymers having a configuration, priorto hydrogenation, of A--B--A wherein each of the A's is analkenyl-substituted aromatic hydrocarbon polymer block and B is abutadiene polymer block wherein 35-55 mol percent of the condensedbutadiene units in the butadiene polymer block have 1,2 configuration.

These selectively hydrogenated ABA block copolymers are deficient inmany applications in which adhesion is required due to their hydrocarbonnature. Examples include the toughening and compatibilization of polarpolymers such as the engineering thermoplastics, the adhesion to highenergy substrates of hydrogenated block copolymer elastomer basedadhesives, sealants and coatings, and the use of hydrogenated elastomerin reinforced polymer systems. However, the placement onto the blockcopolymer of functional groups which can provide interactions notpossible with hydrocarbon polymers solves the adhesion problem andextends the range of applicability of this material.

Beyond the very dramatic improvement in interface adhesion in polymerblends, a functionalized S-EB-S component can also contributesubstantially to the external adhesion characteristics often needed inpolymer systems. These include adhesion to fibers and fillers whichreinforce the polymer system; adhesion to substrates in adhesives,sealants, and coatings based on functionalized S-EB-S polymers, adhesionof decorations such as printing inks, paints, primers, and metals ofsystems based on S-EB-S polymers; participation in chemical reactionssuch as binding proteins such as heparin for blood compatibility;surfactants in polar-nonpolar aqueous or non-aqueous dispersions.

Functionalized S-EB-S polymer can be described as basically commerciallyproduced S-EB-S polymers which are produced by hydrogenation of S-B-Spolymer to which is chemically attached to either the styrene or theethylene-butylene block, chemically functional moieties.

Many attempts have been made for the purpose of improving adhesiveness,green strength and other properties by functionalizing block copolymers,and various methods have been proposed for functionalizing syntheticconjugated diene rubbers.

Saito et al in U.S. Pat. Nos. 4,292,414 and 4,308,353 describe amonovinyl aryl/conjugated diene block copolymer with low 1,2 contentgrafted with a maleic acid compound. However, the process is limited toreaction conditions wherein the generation of free radicals issubstantially inhibited by using free radical inhibitors or conventionalstabilizers for example phenol type phosphorous type or amine typestabilizers. The processes are limited to thermal addition reactions orthe so-called "ENE" reaction. This reaction scheme depends onunsaturation in the base polymer for reaction sites. A reasonable amountof residual unsaturation must be present in order to obtain anadvantageous degree of functionality or grafting onto the base polymer.A substantially completely hydrogenated base polymer would not reactappreciably in the Saito et al process.

Hergenrother et al in U.S. Pat. No. 4,427,828 describe a similarmodified block copolymer with high 1,2 content however, again producedby the `ENE` reaction.

The `ENE` process as described in the prior art results in a modifiedpolymer product which is substituted at a position on the polymerbackbone which is allylic to the double bond. The reaction can be shownfor maleic anhydride as follows: ##STR1## wherein a) represents additionacross a double bond in the main chain of the base polymer and b)represents addition across a double bond occurring in a side chain.After addition and isomerization the substitution is positioned on acarbon allylic to the double bond.

The allylically substituted polymers are prone to thermal degradationdue to their thermal instability. It is known in the art that allylicsubstituents can undergo what has been referred to as a retro-ENEreaction, see B. C. Trivedi, B. M. Culbertson, Maleic Anhydride, (PlenumPress, New York, 1982) pp. 172-173.

Further, because the ENE reaction requires a reasonable amount ofunsaturation in the precursor base polymer, as discussed previously, theresulting functionalized copolymer product will have a significantamount of residual unsaturation and will be inherently unstable tooxidation.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a thermally stablemodified selectively hydrogenated high 1,2 content block copolymer towhich a functional group has been grafted primarily in the vinylareneblock.

More specifically there is provided a functionalized selectivelyhydrogenated block copolymer of the formula B_(n) (AB)_(o) A_(p) wheren=0,1,o=1,2 . . . ; p=0,1 to which has been grafted at least oneelectrophilic graftable molecule or electrophile wherein substantiallyall of said graftable molecules are grafted to the block copolymer inthe vinylarene block.

More preferably there is provided a functionalized selectivelyhydrogenated block copolymer of the formula B_(n) (AB)_(o) A_(p) wheren=0,1,o=1,2 . . . ; p=0,1 to which has been grafted an electrophilicgraftable molecule or electrophile wherein

(1) each A is predominantly a polymerized monoalkenyl aromatichydrocarbon block having an average molecular weight of about 1,000 to115,000;

(2) each B prior to hydrogenation is predominantly a polymerizedconjugated diene hydrocarbon block having an average molecular weight ofabout 20,000 to 450,000;

(3) the blocks A constituting 1-95 weight percent of the copolymer;

(4) the unsaturation of the block B is less than 10% of the originalunsaturation;

(5) the unsaturation of the A blocks is above 50% of the originalunsaturation;

(6) the grafted molecule contains functional groups;

(7) and substantially all of the grafted molecules are grafted to theblock copolymer in the vinylarene block.

The feature of this invention lies in providing modified blockcopolymers which are thermally stable; have a low residual unsaturation,are excellent in appearance characteristics, melt-flow characteristics,and mechanical properties such as tensile strength and impactresistance; etc.

The modified block copolymers according to the present invention aresubstituted in the vinylarene block as shown in the exemplary reactionsgiven below: ##STR2##

The structure of the substituted block copolymer specifically determinedby the location of the functionality on the polymer backbone in thevinylarene block gives the block copolymer a substantially greaterdegree of thermal stability.

DETAILED DESCRIPTION OF THE INVENTION Selectively Hydrogenated BlockCopolymer Base Polymer

Block copolymers of conjugated dienes and vinyl aromatic hydrocarbonswhich may be utilized include any of those which exhibit elastomericproperties and those which have 1,2-microstructure contents prior tohydrogenation of from about 7% to about 100%. Such block copolymers maybe multiblock copolymers of varying structures containing various ratiosof conjugated dienes to vinyl aromatic hydrocarbons including thosecontaining up to about 60 percent by weight of vinyl aromatichydrocarbon. Thus, multiblock copolymers may be utilized which arelinear or radial symetric or asymetric and which have structuresrepresented by the formulae A--B, A--B--A, A--B--A--B, B--A, B--A--B,B--A--B--A, (AB)₀,1,2 . . . BA and the like wherein A is a polymer blockof a vinyl aromatic hydrocarbon or a conjugated diene/vinyl aromatichydrocarbon tapered copolymer block and B is a polymer block of aconjugated diene.

The block copolymers may be produced by any well known blockpolymerization or copolymerization procedures including the well knownsequential addition of monomer techniques, incremental addition ofmonomer technique or coupling technique as illustrated in, for example,U.S. Pat. Nos. 3,251,905; 3,390,207; 3,598,887 and 4,219,627. As is wellknown in the block copolymer art, tapered copolymer blocks can beincorporated in the multiblock copolymer by copolymerizing a mixture ofconjugated diene and vinyl aromatic hydrocarbon monomers utilizing thedifference in their copolymerization reactivity rates. Various patentsdescribe the preparation of multiblock copolymers containing taperedcopolymer blocks including U.S. Pat. Nos. 3,251,905; 3,265,765;3,639,521 and 4,208,356 the disclosures of which are incorporated hereinby reference.

Conjugated dienes which may be utilized to prepare the polymers andcopolymers are those having from 4 to 8 carbon atoms and include1,3-butadiene, 2-methyl-l,3-butadiene (isoprene),2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like.Mixtures of such conjugated dienes may also be used. The preferredconjugated diene is 1,3-butadiene.

Vinyl aromatic hydrocarbons which may be utilized to prepare copolymersincludes tyrene, o-methyl styrene, p-methyl styrene, p-tert-butylstyrene, 1,3-dimethyl styrene, alpha-methyl styrene, vinylnaphthalene,vinylanthracene and the like. The preferred vinyl aromatic hydrocarbonis styrene.

It should be observed that the above-described polymers and copolymersmay, if desired, be readily prepared by the methods set forth above.However, since many of these polymers and copolymers are commerciallyavailable, it is usually preferred to employ the commercially availablepolymer as this serves to reduce the number of processing steps involvedin the overall process. The hydrogenation of these polymers andcopolymers may be carried out by a variety of well established processesincluding hydrogenation in the presence of such catalysts as RaneyNickel, noble metals such as platinum, palladium and the like andsoluble transition metal catalysts. Suitable hydrogenation processeswhich can be used are ones wherein the diene-containing polymer orcopolymer is dissolved in an inert hydrocarbon diluent such ascyclohexane and hydrogenated by reaction with hydrogen in the presenceof a soluble hydrogenation catalyst. Such processes are disclosed inU.S. Pat. Nos. 3,113,986 and 4,226,952, the disclosures of which areincorporated herein by reference. The polymers and copolymers arehydrogenated in such a manner as to produce hydrogenated polymers andcopolymers having a residual unsaturation content in the polydiene blockof from about 0.5 to about 20 percent of their original unsaturationcontent prior to hydrogenation.

Graftable Compounds

In general, any materials having the ability to react with the lithiatedbase polymer, are operable for the purposes of this invention.

In order to incorporate functional groups into the base polymer,monomers capable of reacting with the base polymer are necessary.Monomers may be polymerizable or nonpolymerizable, however, preferredmonomers are nonpolymerizable or slowly polymerizing.

The class of preferred electrophiles which will form graft polymerswithin the scope of the present invention include reactants from thefollowing groups carbon dioxide, ethylene oxide, aldehydes, ketones,carboxylic acid salts, then esters and halides, epoxides, sulfur, boronalkoxides, isocyanates and various silicon compounds.

These electrophiles may contain appended functional groups as in thecase of N,N-dimethyl-p-amino benzaldehyde where the amine is an appendedfunctional group and the aldehyde is the reactive electrophile.Alternatively, the electrophile may react to become the functional siteitself; as an example, carbon dioxide (electrophile) reacts with themetalated polymer to form a carboxylate functional group. By theseroutes, polymers could be prepared containing grafted sites selectedfrom one or more of the following groups of functionality typecarboxylic acids, their salts and esters, ketones, alcohols andalkoxides, amines, amides, thiols, borates, and functional groupscontaining a silicon atom.

These functionalities can be subsequently reacted with other modifyingmaterials to produce new functional groups. For example, the graftedcarboxylic acid described above could be suitably modified byesterifying the resulting acid groups in the graft by appropriatereaction with hydroxy-containing compounds of varying carbon atomslengths. In some cases, the reaction could take place simultaneouslywith the grafting process but in most examples it would be practiced insubsequent post modification reaction.

The grafted polymer will usually contain from 0.02 to 20, preferably 0.1to 10, and most preferably 0.2 to 5 weight percent of grafted portion.

The block copolymers, as modified, can still be used for any purpose forwhich an unmodified material (base polymer) was formerly used. That is,they can be used for adhesives and sealants, or compounded and extrudedand molded in any convenient manner.

Preparation of the Polymers

The polymers may be prepared by any convenient manner one of which isdescribed in copending U.S. application Ser. No. (K-4723) which isherein incorporated by reference.

An example of a method to incorporate functional groups into the basepolymer primarily in the vinylarene block is metalation.

Metalation is carried out by means of a complex formed by thecombination of a lithium component which can be represented byR'(Li)_(x) with a polar metalation promoter. The polar compound and thelithium component can be added separately or can be premixed orpre-reacted to form an adduct prior to addition to the solution of thehydrogenated copolymer. In the compounds represented by R'(Li)_(x), theR' is usually a saturated hydrocarbon radical of any length whatsoever,but ordinarily containing up to 20 carbon atoms, and can be aromaticradical such as phenyl, napthyl, tolyl, 2-methylnaphthyl, etc., or asaturated cyclic hydrocarbon radical of e.g. 5 to 7 carbon atoms, amono-unsaturated cyclic hydrocarbon radical of 5 to 7 carbon atoms, anunconjugated, unsaturated aliphatic hydrocarbon radical of 2 to 20carbon atoms, or an alkyllithium having one or more aromatic groups onthe alkyl group, the alkyl group containing 1 to 20 carbon atoms. In theformula, R'(Li)_(x) x is an integer of 1 to 3. Representative speciesinclude, for example: methyllithium, isopropyllithium, sec-butyllithium,n-butyllithium, t-butyllithium, n-dodecyllithium, 1,4-dilithiobutane,1,3,5-trilithiopentane, and the like. The lithium alkyls must be morebasic than the product metalated alkyl. Of course, other alkali metal oralkaline earth metal alkyls could be used but the lithium alkyls arepreferred due to their ready commercial availability. In a similar way,metal hydrides could be employed as the metalation reagent but thehydrides have only limited solubility in the appropriate solvents.Therefore, the metal alkyls are preferred and their greater solubilitywhich makes them easier to process.

Lithium compounds alone usually metalate copolymers containing aromaticand olefinic functional groups with considerable difficulty and underhigh temperatures which may tend to degrade the copolymer. However, inthe presence of tertiary diamines and bridgehead monoamines, metalationproceeds rapidly and smoothly. Some lithium compounds can be used aloneeffectively, notably the methyllithium types.

It has been shown that the metalation occurs at a carbon to which anaromatic group is attached, or in an aromatic group, or in more than oneof these positions. In any event, it has been shown that a very largenumber of lithium atoms are positioned variously along the polymerchain, attached to internal carbon atoms away from the polymer terminalcarbon atoms, either along the backbone of the polymer or on groupspendant therefrom, or both, in a manner depending upon the distributionof reactive or lithiatable positions. This distinguishes the lithiatedcopolymer from simple terminally reactive polymers prepared by using alithium or even a polylithium initiator in polymerization thus limitingthe number and the location of the positions available for subsequentattachment. With the metalation procedure described herein, the extentof the lithiation will depend upon the amount of metalating agent usedand/or the groups available for metalation. The use of a more basiclithium alkyl such as tert-butyllithium alkyl may not require the use ofa polar metallation promoter.

The polar compound promoters include a variety of tertiary amines,bridgehead amines, ethers, and metal alkoxides.

The tertiary amines useful in the metalation step have three saturatedaliphatic hydrocarbon groups attached to each nitrogen and include, forexample:

(a) Chelating tertiary diamines, preferably those of the formula (R²)₂N-C_(y) H_(2y) --N(R²)₂ in which each R² can be the same or differentstraight- or branched-chain alkyl group of any chain length containingup to 20 carbon atoms or more all of which are included herein and y canbe any whole number from 2 to 10, and particularly the ethylene diaminesin which all alkyl substituents are the same. These include, forexample: tetramethylethylenediamine, tetraethylethylenediamine,tetradecylenediamine, tetraoctylhexyienediamine, tetra-(mixed alkyl)ethylene diamines, and the like.

(b) Cyclic diamines can be used, such as, for example, theN,N,N',N'-tetraalkyl 1,2-diamino cyclohexanes, the N,N,N',N'-tetraalkyl1,4-diamino cyclohexanes, N,N'-dimethylpiperazine, and the like.

(c) The useful bridgehead diamines include, for example, sparteine,triethylenediamine, and the like.

Tertiary monoamines such as triethylenediamine are generally not aseffective in the lithiation reaction. However, bridgehead monoaminessuch as 1-azabicyclo[2.2.2]octane and its substituted homologs areeffective.

Ethers and the alkali metal alkoxides are presently less preferred thanthe chelating amines as activators for the metalation reaction due tosomewhat lower levels of incorporation of functional group containingcompounds onto the copolymer backbone in the subsequent graftingreaction.

In general, it is most desirable to carry out the lithiation reaction inan inert solvent such as saturated hydrocarbons. Aromatic solvents suchas benzene are lithiatable and may interfere with the desired lithiationof the hydrogenated copolymer. The solvent/copolymer weight ratio whichis convenient generally is in the range of about 5:1 to 20:1. Solventssuch as chlorinated hydrocarbons, ketones, and alcohols, should not beused because they destroy the lithiating compound.

Polar metalation promotors may be present in an amount sufficient toenable metalation to occur, e.g. amounts between 0.01 and 100 or morepreferably between 0.1 to about 10 equivalents per equivalent of lithiumalkyl.

The equivalents of lithium employed for the desired amount of lithiationgenerally range from such as about 0.001-3 per vinyl arene unit in thecopolymer, presently preferably about 0.01-1.0 equivalents per vinylarene unit in the copolymer to be modified. The molar ratio of activelithium to the polar promoter can vary from such as 0.01 to 10.0. Apreferred ratio is 0.5.

The amount of alkyl lithium employed can be expressed in terms of theLi/vinylarene molar ratio. This ratio may range from a value of 1 (onelithium alkyl per vinylarene unit) to as low as 1×10⁻³ (1 lithium alkylper 1000 vinylarene units).

The process of lithiation can be carried out at temperatures in therange of such as about -70° C. to +150° C., presently preferably in therange of about 25° C. to 60° C., the upper temperatures being limited bythe thermal stability of the lithium compounds. The lower temperaturesare limited by considerations of production cost, the rate of reactionbecoming unreasonably slow at low temperatures. The length of timenecessary to complete the lithiation and subsequent reactions is largelydependent upon mixing conditions and temperature. Generally the time canrange from a few seconds to about 72 hours, presently preferably fromabout 1 minute to 1 hour.

Grafting Step

The next step in the process of preparing the modified block copolymeris the treatment of the lithiated hydrogenated copolymer, in solution,without quenching in any manner which would destroy the lithium sites,with a species capable of reacting with a lithium anion. These speciesmust contain functional groups capable of undergoing nucleophilic attackby a lithium anion. Such species contain functional groups including butnot limited to

    ______________________________________                                         ##STR3##                                                                      ##STR4##                                                                     CORetherCSHThiol                                                               ##STR5##                                                                      ##STR6##                                                                     ______________________________________                                    

The process also includes further chemistry on the modified blockcopolymer. For example, converting of a carboxylic acid salt containingmodified block copolymer to the carboxylic acid form can be easilyaccomplished.

EXAMPLES Example 1

The base polymer used in the following example was an S-E/B-S type blockcopolymer (herein referred to as reactant polymer A). Reactant polymer Ahad a molecular weight of about 50,000 and was 30% polystyrene.

In a typical experiment, 100 lbs of a polymer cement containing PolymerA in cyclohexane (5% solids) was lithiated at 60° C. using a diamine(TMEDA) promoted s-BuLi reagent (1.1 mol base, 1.8 mol promoter). Arapid metalation reaction afforded a thixotropic, semisolid cement whichimmobilized the reactor's stirring mechanism (auger type) within 3-4minutes. An aliquot of the lithiated-polymer cement was quenched with D₂O. The remainder was transferred through a 11/2" diameter line to avessel containing an excess of CO₂ (3 lbs) in tetrahydrofuran (THF). Thecarboxylated product was treated with HOAc (85 g, 1.4 mol) and finishedby steam coagulation affording over 4 lbs of white, functionalizedpolymer crumb. Analyses of the carboxylated product found 0.84% wt --CO₂H and 0.29% wt --CO₂ -- for a total polymer bound carboxylate content of1.13% wt.

A deuterium (D) NMR analysis of the D₂ O treated aliquot found the Dresided primarily at aromatic sites, at meta and para positions on thering, (90% of total D), with the remainder of the tag or label being ateither benzylic or allylic positions (10% of total D). The techniquecannot discern between allylic and benzylic locations. Thus, the labelresided-principally, at least 90%, and most likely entirely in thepolystyrene block of the polymer. We infer from this labellingexperiment that essentially all of the lithiation reaction, at least90%, occurred in the polystyrene block. Therefore, essentially all ofthe carboxylation must occur at these sites as well.

For this experiment, 50% of the reactant s-BuLi was converted intopolymer bound carboxylate as found in the product (lithiationefficiency). The product, as finished, contained 74 parts of acid (--CO₂H ) to every 26 parts of salt (--CO₂ --).

Examples 2-14

Examples 2-14 were conducted as outlined in Example 1. Somemodifications were used as outlined in Table 1.

Reactant polymer B was similar to polymer A with the molecular weightbeing about 67,000. Reactant polymer C was similar to polymer A with themolecular weight being about 181,000 and a polystyrene content of 33%.Reactant polymer D was an S-E/P type of block copolymer with a totalmolecular weight of about 98,000 and a polystyrene content of 37%.

The lithiation of polymers A, B and C proceeded with a rapid rise inviscosity in all examples. In some examples, the lithiated product wasallowed to digest for longer periods without stirring. The lithiation ofpolymer D proceeded with no observable increase in cement viscosity.

As found in Example 1, deuterium NMR analyses of D₂ O quenched aliquotsof the various products found the label to be predominately in thepolystyrene block of the polymer. These results are summarized in Table2.

Each of the deuterated samples was analyzed by Gel PermeationChromatography. The resulting molecular weight information did notdiffer significantly from that for the starting unmetalated polymer.This indicates that the metalation technique did not induce anydegradation, for example, chain scission or crosslinking in thesepolymers.

Control experiments using the reaction technique of Example 1 andS-rubber-S block copolymers where the rubber is substantiallyunsaturated showed that these reactants were lithiated indiscriminatelyin both the styrene block (about 50%) and the rubber block (about 50%).These randomly functionalized products were not preferred.

                                      TABLE I                                     __________________________________________________________________________    PREPARATION OF KRATON.sup.R G POLYMER CONTAINING                              LITHIUM CARBOXYLATE FUNCTIONALITY                                             Reaction Conditions                                                                              Product Analysis                                                         Reaction                                                                           Carboxylate Content                                                                          Lithiation                                                                          Acid/Salt                             Polymer    .sub.- s-Bu-Li                                                                   Time (% wt)         Efficiency                                                                          As Finished                           Example                                                                            type (mol)                                                                             (min)                                                                              Theory                                                                            As Finished                                                                         Acidified                                                                          %     Polymer                               __________________________________________________________________________    2    A    1.13                                                                              60   2.25                                                                              1.12  1.39 62    81/19                                 3    A    1.13                                                                              60   2.25                                                                              0.21  0.22 10    95/5                                  4    A    1.13                                                                              60   2.25                                                                              0.60  1.04 46    58/42                                 5    B    1.13                                                                               1   2.25                                                                              --    0.94 42    10/90                                 6    B    1.13                                                                               2   2.25                                                                              0.13  1.00 44    13/87                                 7    B    0.38                                                                              60   0.75                                                                              0.46  0.43 58    99/1                                  8    B    0.38                                                                              60   0.75                                                                              0.28  0.27 36    99/1                                  9    C    0.38                                                                               4   0.75                                                                              0.22  0.33 44    67/33                                 10   C    0.38                                                                              10   0.75                                                                              0.31  0.33 46    94/6                                  11   D    1.13                                                                              60   2.25                                                                              0.92  1.15 51    80/20                                 12   D    1.13                                                                              30   2.25                                                                              0.36  0.24 11    99/1                                  13   D    1.13                                                                              60   2.25                                                                              1.15  1.39 62    83/17                                 14   B    0.9 150  --  0.44  --   --    --                                    __________________________________________________________________________

                  TABLE II                                                        ______________________________________                                        Location of Deuterated Site                                                            Location of Deuterium Label (Carboxylate)                            Example    Aromatic     Benzylic, Allylic                                     Number     (%)          (%)                                                   ______________________________________                                        2          91           9                                                     3          93           7                                                     4          92           8                                                     ______________________________________                                    

Example 15

The modified block copolymer in Example 14 was converted to thecarboxylic acid salt formed by the following procedure: 50 gms ofpolymer was dissolved in 500 gms of a 90:10 mixture of cyclohexane:THF.Next, 4.3 gms of a 1 molal aqueous LiOH solution was added. The mixturewas allowed to stand 24 hours. The polymer was then recovered byprecipitation with methanol and dried under vacuum. By IR analysis, thesample showed complete conversion of acid functionality to lithium saltfunctionality. The absorbance band of the salt occurs at 1560-1600 cm⁻¹while that of the acid occurs at 1690 cm⁻¹.

Example 16

In this example, hydroxyl functionality was placed on the base polymer.The base polymer used was Reactant Polymer B.

100 gms of the base polymer was dissolved in 100 ml of cyclohexane in aglass reactor under an argon purge. 1.02 meq TMEDA per gm of polymer wasthen added. Impurities in the mixture were then removed by titrationwith sec-butyllithium. The reactor contents were heated to 50° C., and0.51 meq of additional sec-butyllithium per gm of polymer were added.1000 ml of distilled THF was added and this solution was stirred at 25°C. for 16 hours. This mixture was maintained at 40°-45° C. for 70minutes. Next, ethylene oxide was bubbled into the vessel and themixture was stirred for 10 minutes at 45° C. Finally, 1 meq of HCl (inmethanol) per gm of polymer was added to the reactor. The polymer wasrecovered by coagulation into isopropanol and washed with methanol. Aportion of the polymer was dried under vacuum at 40° C.

In order to analyze this hydroxylated polymer, the OH functionality wasconverted to acid by reaction with maleic anhydride at 150°-160° C. indiisopropylbenzene. The reaction product was precipitated into methanoland washed with 70° C. water to remove unreacted maleic anhydride. IRmeasurement showed carbonyl bands at 1730 cm⁻¹ characteristic of amaleic ester.

The polymer was then dried under vacuum at 50° C. Titration for the halfmaleic acid ester using potassium methoxide in methanol together with aphenolphthalein indicator gave 0.18 meq acid per gm polymer, showingthat the original modified block copolymer contained 0.18 meq OH groupsper gm polymer.

What is claimed is:
 1. A functionalized selectively hydrogenated blockcoplymer of the formula B_(n) (AB)_(o) A_(p) where n=0 or 1, o=1 or 2,p=0 or 1, A is predominately a polymerized monalkenyl aromatichydrocarbon block and B prior to hydrogenation is predominately apolymerized conjugated diene hydrocarbon block to which has been graftedcarbon dioxide wherein substantially all of the carbon dioxide moleculesare grafted to the block copolymer in the monoalkenyl aromatichydrocarbon blocks.
 2. A functionalized selectively hydrogenated blockcopolymer of the formula B_(n) (AB)_(o) A_(p) where n=0 or 1, o=1 or 2,p=0 or 1, A is predominately a polymerized monoalkenyl aromatichydrocarbon block and B prior to hydrogenation is predominantely apolymerized conjugated diene hydrocarbon block to which has been graftedan electrophilic graftable molecule or electrophile wherein(1) each A ispredominantly a polymerized monalkenyl aromatic hydrocarbon block havingan average molecular weight of about 100 to 115,000; (2) each B prior tohydrogenation is predominantly a polymerized conjugated dienehydrocarbon block having an average molecular weight of about 20,000 to450,000; (3) the blocks A constituting 1-95 weight percent of thecopolymer; (4) the unsaturation of the block B is less than 10% of theoriginal unsaturation; (5) the unsaturation of the A blocks is above 50%of the original unsaturation; (6) the grafted molecule containsfunctional groups; (7) substantially all of the grafted molecules aregrafted to the block copolymer in the vinylarene block; (8) and saidelectrophile is selected from the groups consisting of carbon dioxide,carboxylic acids and their salts and esters.
 3. The functionalized blockcopolymer of claim 1 wherein the block copolymer is astyrene-ethylene/butylene-styrene block copolymer.
 4. The blockcopolymer of claim 1 wherein prior to hydrogenation, the polymericblocks A are polymer blocks of a monoalkenyl aromatic hydrocarbon. 5.The block copolymer of claim 1 wherein the blocks A comprise 1-40percent by weight of the copolymer, the unsaturation of block B isreduced to less than 5% of its original value and the averageunsaturation of the hydrogenated block copolymer is reduced to less than20% of its original value.
 6. The block copolymer of claim 5 wherein Ais a polymerized styrene block having an average molecular weight ofbetween about 500 and 60,000.
 7. The block copolymer of claim 1 whereinB is a polymerized butadiene block having an average molecular weigh ofbetween about 35,000 and 150,000, 35%-50% of the condensed butadieneunits having 1,2-configuration.
 8. The block copolymer of claim 7wherein the unsaturation of block B has been reduced by hydrogenation toless than 10% of its original value.
 9. A functionalized selectivelyhydrogenated block copolymer composition according to claim 1 wherein anaverage of less than about 20% of the monoalkenyl aromatic hydrocarbonunits are hydrogenated.
 10. A functionalized hydrogenated blockcopolymer composition according to claim 1 wherein an average of morethan about 25% of the monoalkenyl aromatic hydrocarbon units arehydrogenated.
 11. The functionalized hydrogenated block copolymer ofclaim 1 wherein the grafted molecule or its derivative is present in thefunctionalized block copolymer at between about 0.02-20 weight percent.12. The functionalized hydrogenated block copolymer of claim 1 whereinthe grafted molecule or its derivative is present in the functionalizedblock copolymer at between about 0.1-10 weight percent.
 13. Thefunctionalized hydrogenated block copolynmer of claim 1 wherein thegrafted molecule or its derivative is present in the functionalizedblock copolymer at between about 0.2-5 weight percent.